In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of achieving higher-speed data rates, providing low delay and so on, long-term evolution (LTE) has been standardized (see Non Patent Literature 1). For the purposes of achieving further broadbandization and higher speed beyond LTE, LTE advanced has been standardized (Rel. 10-12), and further successor systems to LTE called 5G (5th Generation Mobile Communication System), FRA (Future Radio Access) and so on have been also studied.
In future radio communication systems (e.g., 5G), due to their use for mobile broadband, it is assumed that there will be a demand for further increases in speed and volume, while being required to reduce delay and deal with the connecting of a large volume of devices. Furthermore, in order to achieve a further increase in speed and volume, it is also envisaged that an even broader bandwidth of the frequency spectrum will be utilized.